You are not the only ones. Apparently AT&T and Yahoo web hosting have split. and if you did not sign the new terms and conditions, the account was deactivated. We have also had our business's website down and emails gone since the weekend.
01:39 PM PST: Customers are unable to reach Yahoo Small Business
At this time we are receiving extremely high call volume which is limiting our ability to answer your call within our expected handle times. If you are a small business customer requiring help with your account, we highly encourage you to hang up and log into your account, and request assistance through our on line service request form which is the quickest current contact method as your account will be considered verified and the process will move forward at an expedited pace. We are also asking small business customers to not use our automated call back feature as it is currently undergoing unplanned system maintenance and is not currently available. If you are unable to log into your account at this time, you may send an email with details of the issue you are experiencing to firstname.lastname@example.org and we will work to resolve your issue in the order in which it is received.